The present invention relates to a semiconductor device and manufacturing method thereof, and particularly to effective technology applied to a semiconductor device having capacitive elements using an insulating film made from metallic oxide as a capacitive insulation film and a manufacturing method thereof.
In the related art, DRAMs (Dynamic random access memory) provided with transistors and capacitors are a typical example of a semiconductor storage device.
Capacitors constituting a DRAM are made of an upper electrode and a lower electrode, and a capacitive insulation film provided between these two electrodes. An insulation film made from a silicon compound such as a silicon oxide film or a nitride film is generally used as this capacitive insulation film
Also at the present time, the use of high dielectric film or ferroelectric films, having smaller surface area but large capacitance compared to conventional capacitive insulation film made of silicon oxide or silicon nitride, as a capacitive film of a capacitor is being investigated.
Of these films, a capacitor having a ferroelectric film as a capacitive insulation film is used in the formation of semiconductor storage devices known as FeRAM (Ferroelectric random access memory).
FeRAM are non-volatile semiconductor storage devices capable of obtaining the same read speed and write speed as for a conventional DRAM. For this reason they are being noted as future semiconductor memory devices.
Insulating film made from metallic compounds, such as bismuth strontium titanate (SrBi2Ta2O9) called SBT or zirconium lead titanate called PZT, are used in capacitive insulating films of capacitors constituting a FeRAM. Also, precious metal such as platinum (Pt) is used in upper electrodes and lower electrodes constituting the capacitors. This is exposed to a high temperature oxidizing atmosphere at the time of forming the high strength dielectric film or at the time of membrane improvement of the capacitive insulation film after forming the capacitors, and therefore requires oxidation resistance for the electrode material.
Conventionally, a semiconductor storage device using this type of high strength dielectric film is formed by forming active elements on a semiconductor substrate, and then sequentially forming capacitors having a high strength dielectric film and wiring layers for electrical interconnection, through an interlayer insulation film.
However, with a strong dielectric film made from a metal oxide material included in a semiconductor storage device, such as FeRAM, the formation energy of the oxide material is low compared to a dielectric film formed from a silicon compound included in a conventional semiconductor storage device, and has the property that reduction is easy. Because of this, with formation of a plug for electrically connecting between an inter-layer insulation film and each wiring layer after formation of a capacitor, or a step of exposing a capacitor having a strong dielectric film, for preventing damage to semiconductor elements added in each process etc., to a reducing atmosphere, it is easy for the strong dielectric film to be reduced by hydrogen (H2) or moisture (H2O) contained in the reducing atmosphere. As a result, there are critical problems like deterioration in the film quality of the strong dielectric film, and also degradation to the electrical characteristics of the capacitor.
In a semiconductor storage device including a high strength dielectric film of he related art, a capacitor is used with a protective film for preventing diffusion of H2O from the reducing atmosphere formed on the surface.
The object of the present invention is to provide a more highly reliable semiconductor device, and a method of manufacturing such as device, in which a capacitor using an insulating film made of a metal oxide as a capacitive insulation film has a protective film for sufficiently preventing diffusion of H2, and film quality degradation of the capacitive insulation film due to mutual reaction is prevented.
With a capacitor having the protective film of the related art, mutual reaction inside the reducing atmosphere of a step of a manufacturing process after formation of the capacitor is caused by combining materials of a protective film for preventing diffusion of H2 to a capacitive insulation film made from a metal oxide insulation film, an upper electrode and a lower electrode, and this causes degradation in the film quality of the capacitive insulation film. As a result, with a capacitor having a conventional protective film, there is a problem that it is not possible to obtain sufficient electrical characteristics of the capacitor.
With the present invention, in order to achieve the above described object, a semiconductor device according to one aspect of the present invention comprises a substrate, a lower electrode provided on a surface of this substrate, a capacitive insulation film formed from a metal oxide material formed on this lower electrode, capacitive elements including an upper electrode formed on the capacitive insulation film, a first silicon oxide film covering upper surfaces of the capacitive elements ands formed using a gas containing ozone, a protective film covering over the first silicon oxide film corresponding to upper surfaces of the capacitive elements, and an insulating film arranged on the protective film and having a film thickness thicker than the first silicon oxide film.
Also, in order to solve the problems described above, a semiconductor device according to another aspect of the present invention comprises a substrate, a lower electrode provided on a surface of this substrate, a lower electrode, a capacitive insulation film formed from a metal oxide material formed on this lower electrode, capacitive elements including an upper electrode formed on the capacitive insulation film, and a protective film, for covering upper surfaces of the capacitive elements, having a core element for at least crystallization of the capacitive insulation film, and formed from a metal oxide material having a compositional ratio of a core element for crystallization lower than the compositional ratio of a core element for crystallization included in the capacitive insulation film.
In addition, a method of manufacturing a semiconductor device according to one aspect of the present invention comprises the steps of forming capacitive elements, including a lower electrode, a capacitive insulating film formed from a metal oxide material formed on the lower electrode, and an upper electrode formed on the capacitive insulation film, on the surface of a substrate, a step of forming a first silicon oxide film by a chemical vapor phase deposition method using a gas containing ozone, a step of subjecting the first silicon oxide film to heat treatment after formation of the first silicon oxide film, a step of forming a protective film on the first silicon oxide film subjected to heat treatment and covering upper surfaces of the capacitive elements, and a step of forming an insulating film having a film thickness thicker than the first silicon oxide film on the protective film.
Also, in order to solve the problems described above, a method of manufacturing a semiconductor device according to another aspect of the present invention comprises a step of forming capacitive elements by sequential deposition on a surface of a substrate of a lower electrode, a capacitive insulation film formed from a metal oxide material, and an upper electrode, and a step of forming a protective film, on an upper surface of the substrate including the capacitive elements, having a core element for at least crystallization of capacitive insulation film, and formed from a metal oxide material having a compositional ratio of a core element for at least crystallization lower than the compositional ratio of a core element for at least crystallization included in the capacitive insulation film.
According to the present invention having these structures, it is possible to prevent mutual reaction between the protective film and the capacitor material, and as a result it is possible to provide a semiconductor that does not suffer from degradation of capacitor characteristics.